Broadband low noise amplifier

ABSTRACT

Aspects provide for the broadband amplification of RF signals. Other aspects provide for the conversion of single ended input to differential output. Various aspects provide for tuning the response to a particular frequency band. Other aspects provide for various transconductance elements. In several aspects, broadband current to voltage converters and voltage to current converters are presented. Some implementations incorporate a buffer circuit, and various implementations incorporate feedback circuits.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application60/827,033, “Method and System for Tuned CMOS Low Noise Amplifier,”filed Sep. 26, 2006, which is incorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates generally to the amplification of radiofrequency signals.

2. Description of Related Art

A variety of applications require the amplification of RF (radiofrequency) signals with minimum noise. Signals may be received viasingle ended inputs or differential inputs, and often theseamplification processes should be performed with low power.Amplification to high bandwith may also be desirable. Typically, lownoise amplifiers provide for at least some decoupling of the noise ofthe amplification circuit from the impedance of the amplificationcircuit. However, this decoupling often requires high power. Improvedcircuits for transconductance and low noise amplification are needed.

SUMMARY OF THE INVENTION

Embodiments include a transconductance circuit having an n-typetransistor and a p-type transistor, in which the source of the n-typetransistor is connected to the source of the p-type transistor; and oneor more resistive loads are disposed. Each load is connected to thedrain of either the n-type transistor or, the p-type transistor, andeach load allows passage of a current without limiting current. A bridgemay connect one end to at least one source, an input to the circuitconnects to at least one gate, and an output to from the circuitconnects to at least one drain. Input and output connections are made totransistors that are connected to a load.

In other embodiments, transconductance circuits including n-type andp-type transistors are provided. The source of the n-type transistor isconnected to the source of the p-type transistor. One or more resistiveloads are present, and each load is connected to the drain of eithertransistor. Each load allows passage of a current without limitingcurrent. A bridge may connect one end to at least one gate; an input tothe circuit connects to at least one source, and an output from thecircuit connects to at least one drain of a transistor connected to aload.

Various embodiments of transconductance circuits and transconductanceelements may not require a current source.

In various embodiments, bridges of different circuits may be connectedto each other. In other embodiments, bridges connect differentcomponents of two different transistors (e.g. a source of one transistorto a gate of another transistor). In various embodiments, bridges mayinclude a tune block having an impedance.

In certain embodiments, tuning is provided for by the incorporation of atune block in a bridge, feedback circuit, input and/or output, and incertain cases, the tune block may be physically disposed outside of thechip upon which the circuit is fabricated.

Some embodiments provide for a cross coupled transconductance elementhaving an input and output. The transconductance element is composed oftwo transconductance circuits, and each circuit includes both n-type andp-type transistors, and the source of the n-type transistor is connectedto the source of the p-type transistor. An input to the transconductanceelement connects to at least one source, and output to thetransconductance element connects to at least one drain. The drains ofthe transistors are connected, as are the gates. A bridge connects agate of the first circuit to a source of the second circuit, and anotherbridge connects a gate of the second circuit to the source of the firstcircuit. In some implementations, devices can be used as single ended todifferential converters. In other implementations, devices can providenoise cancellation. In various embodiments, a tune block having animpedance can be incorporated.

Certain embodiments provide for a tuned transconductance element havingan input and an output. The transconductance element includes twotransconductance circuits, each of which contains an n-type and a p-typetransistor. An input to the element connects to at least one gate, andan output to the element connects to at least one drain. In eachcircuit, the drain of the n-type transistor is connected to the drain ofthe p-type transistor, and the gate of the n-type transistor isconnected to the gate of the p-type transistor. A bridge connects asource of one circuit to a source of the other circuit, and in someembodiments, this bridge may include a tune block having an impedance.

Various embodiments provide for a tuned transconductance elementincluding a first and second transconductance circuit. Each circuitincludes a first n-type transistor and a second n-type transistor, andan input to the element connects to the gate of the first transistor. Anoutput to the element connects to the drain of the first transistor. Thesource of the first transistor is connected to the drain of the secondtransistor at a junction. A resistor connects the drain of the firsttransistor and the gate of the second transistor, and a capacitorconnects the gate of the second transistor and ground. The elementprovides for a bridge connecting the junctions of each transconductancecircuit. In some embodiments, the bridge includes a tune block having animpedance.

Some embodiments provide for a tuned transconductance element includingfirst and second transconductance circuits. Each circuit includes ann-type and a p-type transistor, and the drains of these transistors areconnected. An input to the element connects to at least one source, andan output to the element connects to at least one drain. In eachcircuit, the gate of the n-type transistor is connected to the gate ofthe p-type transistor. The element also includes a bridge connecting atleast one gate of the first circuit to at least one gate of the secondcircuit. In some embodiments, the bridge includes a tune block having animpedance.

Certain embodiments provide for a low noise amplifier. Components ofvarious low noise amplifiers include various transconductance circuitsand transconductance elements. Low noise amplifiers also include one ormore feedback circuits, each of which includes a resistor. Each feedbackcircuit connects an input to an output having opposite polarity. Ingeneral, resistors included in a feedback circuit may be switchableresistors, and in some implementations, the switching of resistance infeedback circuits may be used to modify gain while maintaining impedanceof the device at a desired value. In certain implementations, feedbackcircuits may include a tune block having an impedance. Any of these tuneblocks may be used to tune the circuit, element, amplifier or otherdevice incorporating the tune block. For various implementations, a tuneblock may be located in a location physically disposed away form thecircuitry being tuned.

Certain implementations provide for the incorporation of a buffercircuit with various circuits, elements and amplifiers. In someembodiments, feedback circuits can include feedback around the buffercircuit.

Some embodiments provide for a tuning circuit, used to tune the responseof a circuit to a band of interest, according to the impedance andcapacitance of the tuning circuit. The tuning circuit connects two ormore transistors, by connecting the source, drain or gate of onetransistor to the source, drain or gate of another transistor. Thetuning circuit includes a tune block having an impedance. In variousembodiments, multiple tune circuits are provided, making a parallelconnection between two transistors. By incorporating tune blocks havingdifferent impedances in each tune circuit, the circuit can be tuned torespond to multiple frequency bands, according to the impedance of eachtune circuit. A large number of tune circuits can be incorporated,providing for tuned response in a large number of bands.

Other embodiments provide for a low noise amplifier including a commongate transconductance element. The amplifier also includes two or morefeedback circuits. One feedback circuit connects a positive input to theelement to a negative output, and another feedback circuit connects anegative input to the element of a positive output. Feedback circuitsinclude feedback resistors. Feedback circuits may generally includebypass capacitors. Feedback circuits may also include tune blocks havingan impedance.

Certain embodiments provide for a current to voltage converter. Acurrent to voltage converter can include a common gate transconductanceelement, a common source transconductance element connected to thecommon gate transconductance element, and at least one feedback circuitincluding a feedback resistor and optionally a capacitor. A feedbackcircuit connects at least one input of a transconductance element to anoutput having opposite polarity. In some embodiments, current to voltageconverters also include a buffer circuit, and this buffer circuit mayalso include feedback circuits in connection with other transconductanceelements.

Other embodiments provide for a low noise amplifier including a first,common source transconductance element connected to a common gatetransconductance element. A second common source transconductanceelement is connected to the common gate transconductance element. Atleast one feedback circuit, including a feedback resistor, connects theinput of any transconductance element to the output of anothertransconductance element, the input and output having opposite polarity.Certain embodiments of low noise amplifiers include a buffer circuit,and in some implementations, feedback circuits can include the buffercircuit.

Other implementations provide for a buffer circuit comprising an n-typetransistor and a p-type transistor. The sources of the transistor areconnected by a resistor. The sources are also connected by a capacitor.An input to the circuit connects to at least one gate, and an outputfrom the circuit connects to at least one source.

Various embodiments, provide for a tuned, cross coupled transistorcircuit comprising two transistors. The gate of the first transistor isconnected to the source of the second transistor by a bridge, and thegate of the second transistor is connected to the source of the firsttransistor by a bridge. The bridges include tune blocks, and each tuneblock has an impedance.

Further embodiments provide for an active resistive load circuit,capable of passing current without being current limiting. A circuit mayinclude a transistor having a source connected to either a power supplyor to ground. A capacitor connects the source and the gate of thetransistor, and a resistor connects the gate and drain of thetransistor. A device to which the circuit provides a load may beconnected to the drain of the circuit.

Other embodiments provide for a wrapping circuit. In someimplementations, a wrapping circuit may provide a high impedanceconnection between a device and another component in a circuit such as aground or a power supply. Other aspects may protect the device fromground noise or power supply noise. A wrapping circuit may include atransistor, and the source of the transistor is connected to thecomponent such as ground or power supply. The drain of the transistor isconnected to a first connection of the device being wrapped. Thewrapping circuit also includes a capacitor. The capacitor is connectedon a first end to the component, and connected on a second end to thegate of the transistor. A resistor is connected on a first end to thesecond end of the capacitor, and the resistor is connected on a secondend to a second connection of the device.

Various embodiments of the invention can provide impedance matching toantennae, filters, duplexers or other upstream signal sources. Broadbandamplification and tuned amplification may be provided. In the case oftuned amplification, large components such as inductors can be locatedoff chip. Differential inputs and single ended inputs can be amplified.In the case of single ended input, implementations may be more immune toground noise than other amplifiers and transconductance elements.

Linearity of some transconductance elements may be high, particularly atinputs near zero. Linearity may also be high to high bandwith, and insome cases, this can reduce the manifestation of extra tones in thefrequency domain. In some embodiments of transconductance elements, bothn-type and p-type transistors operate on both positive and negativeinput signals.

Input signals may be amplified with minimal noise addition. For tunedapplications, amplification is only performed in the tuned band; noiseoutside the band is not amplified. Gain may be maintained to highfrequencies, and in some embodiments there is a high signal to noiseratio. Noise generation is done without compromising gain. Aspectsfeature high Q, and additional filtering can be used to further sharpenQ if so desired.

Various embodiments may provide very low output impedance, which can beuseful when combined with downstream components having high frequencynoise. Other embodiments provide for high swing, in some cases from railto rail.

Still further embodiments provide for variable gain, switchable by auser, and devices can be made to operate using low power requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary low noise amplifier having asingle bridge according to one embodiment of the invention.

FIG. 2 is a block diagram of an exemplary low noise amplifier having twobridges according to one embodiment of the invention.

FIG. 3 is a block diagram of an exemplary LNA core according to oneembodiment of the invention.

FIG. 4 is a block diagram of another exemplary LNA core according to oneembodiment of the invention.

FIG. 5 is an exemplary broadband voltage to voltage converter accordingto one embodiment of the invention.

FIG. 6 is an exemplary first gain stage, showing a common source lineartransconductance element according to one embodiment of the invention.

FIGS. 7A, 7B and 7C show several exemplary bridges according to oneembodiment of the invention.

FIG. 8 is another exemplary first gain stage, showing a common sourcetransconductance element according to one embodiment of the invention.

FIG. 9 is yet another exemplary first gain stage, showing a commonsource transconductance element according to one embodiment of theinvention.

FIG. 10 is still another exemplary first gain stage, showing a commonsource transconductance element according to one embodiment of theinvention.

FIG. 11 is a schematic of an exemplary bias circuit according to oneembodiment of the invention.

FIG. 12 is a schematic of an exemplary bias circuit according to oneembodiment of the invention.

FIG. 13 is a schematic of an exemplary bias circuit according to oneembodiment of the invention.

FIG. 14 is a schematic of an exemplary bias circuit according to oneembodiment of the invention.

FIG. 15 is a schematic of an exemplary second gain stage, showing acommon gate linear transconductance element that features a crosscoupling circuit according to one embodiment of the invention.

FIG. 16 is a schematic of another exemplary second gain stage, showing acommon gate linear transconductance element that features a crosscoupling circuit according to one embodiment of the invention.

FIG. 17 is a schematic of yet another exemplary second gain stage,showing a common gate transconductance element according to oneembodiment of the invention.

FIG. 18 is a schematic of still another exemplary second gain stage,showing a common gate transconductance element according to oneembodiment of the invention.

FIG. 19 is a schematic of yet another exemplary second gain stage,showing a common gate transconductance element that features a crosscoupling circuit according to one embodiment of the invention.

FIG. 20 is a schematic of an exemplary third gain stage, showing a pushpull transconductance element according to one embodiment of theinvention.

FIG. 21 is schematic of an exemplary LNA circuit that also includes abuffer stage according to one embodiment of the invention.

FIG. 22 is a schematic of an exemplary buffer stage according to oneembodiment of the invention.

FIG. 23 is a schematic of an exemplary broadband voltage to voltageconverter, having a first gain stage designed for single ended input,combined with a single ended to differential converter according to oneembodiment of the invention.

FIG. 24 is a schematic of an exemplary first gain stage for a singleended input according to one embodiment of the invention.

FIG. 25 is a schematic of another exemplary first gain stage for asingle ended input according to one embodiment of the invention.

FIG. 26 is a schematic of a broadband current to voltage converterincorporating first and second gain stages, bias circuits, feedbackcircuits, transistor loading circuits and optional cross couplingcircuits according to one embodiment of the invention.

FIG. 27 is a schematic of a common source transconductance elementaccording to one embodiment of the invention.

FIG. 28 is a schematic of a common gate transconductance elementaccording to one embodiment of the invention.

FIG. 29A is a block diagram of a common source transconductance elementincorporating a bridge and feedback circuits according to one embodimentof the invention.

FIG. 29B is a block diagram of another common source transconductanceelement incorporating a bridge and feedback circuits according to oneembodiment of the invention.

FIG. 30 is a block diagram of a broadband voltage to voltage converteraccording to one embodiment of the invention.

FIG. 31A is a block diagram showing a combination of an exemplary commongain transconductance element with a feedback circuit.

FIG. 31B is a block diagram showing an exemplary broadband voltage tovoltage converter (e.g. for use in BBI2V 3010) incorporating feedbackcircuits.

DETAILED DESCRIPTION OF THE INVENTION

Typically, broadband amplification of radio frequency signals (aftertheir having been received by an appropriate antenna device) refers toamplification over a range of frequencies much larger than the typicalband of frequencies associated with a specific communications protocol(e.g. the analog TV band, the CDMA band, the GSM band, the GPS band, the802.11 band and the like). Thus, “broadband” includes frequencies fromfractions of 1 Hz to at least 4 GHz. The present invention can extendamplification far beyond 4 GHz, and is presently limited by the processtechnology used for circuit manufacture (e.g. CMOS process technologyfor CMOS circuitry). As process technology improves, the invention isexpected to amplify signals at 6 GHz, 12 GHz, 24 GHz or even higherfrequencies.

FIG. 1 is a block diagram of Low Noise Amplifier (LNA) 100 according toone embodiment of the present invention. LNA 100 includes LNA Core 110,which includes Feedback Components 180, and Bridge 170. In this example,a portion of Bridge 170 is inside LNA Core 110 and a portion is outsideLNA Core 110. In general, each amplifying component such as a low noiseamplifier (LNA), op-amp, transconductance element and the like isdemarcated herein using standard (+) and (−) symbols to denote inversion(or lack thereof) performed by the device on a given input signal priorto output.

Package 102 comprises LNA Core 110 and several Pads 120 providing pointsof electrical contact to Package 102 from the outside of Package 102. Inthis example, Pads 120 provide for the input of A/C signals as well asconnection to part of Bridge 170 located outside Package 102. Thus, aportion of Bridge 170 passes outside Package 102 in this example. Bridge170 includes Capacitor 162 and Tune Block 172. For illustrativepurposes, several possible locations for Capacitor 162 and Tune Block172 are shown in FIG. 1. Bridge 170 may include Capacitor 162 and TuneBlock 172 located outside of LNA Core 110, although any and/or all ofthese components may be located inside LNA Core 110, located on Package102, or located outside of Package 102 as desired. Thus, FIG. 26 showslocations of Tune Block 172 and Capacitor 162 as part of Package 102 andas part of LNA Core 110, although typical instances of Bridge 170 wouldnot necessarily have all of these components in all of the locationsillustrated on FIG. 1.

Tune Block 172 can have zero impedance (i.e. be a simple connection)providing for broadband amplification. For tuned applications, TuneBlock 172 can include an impedance circuit, and/or may include aninductor. For some embodiments of Tune Block 172 including impedancecircuits, it may be convenient to locate Tune Block 172 outside ofPackage 102. Bridge 170 can include other components (e.g. capacitors)that may be located either outside Package 102 or inside Package 102, oreven on the same chip as LNA Core 110. Although Bridge 170 may be usedto tune LNA 100 to a specific frequency band, Bridge 170 performs otherfunctions also, and so is generally a component of LNA 100 even thoughLNA 100 may be used for broadband amplification (i.e. not be tuned).

FIG. 1 also illustrates several alternative options for theincorporation of tuning. Tune Block 172 and Capacitor 162 can beincorporated into either or both of the input signal paths. In FIG. 1,an example of this incorporation is illustrated by the optionalincorporation of Tune Block 172 and Capacitor 162 in the In+ 130 signalpath. As discussed later, tune blocks such as Tune Block 172 andcapacitors such as Capacitor 162 may also be incorporated into one ormore feedback circuits. In any of these tuning configurations, TuneBlock 172 and/or Capacitor 162 may be incorporated onto the chip uponwhich LNA Core 110 is fabricated, onto Package 102, or outside Package102. Additionally, other amplifiers, transconductance elements,transimpedance elements or other circuitry can also be modified toprovide tuned response by the incorporation of any of the embodiments ofTune Block 172 and/or Capacitor 162 described herein.

Positive voltage input In+ 130 is an input to LNA Core 110. Negativevoltage input In− 140 is another input to LNA Core 110. In+ 130 and In−140 receive input signals (e.g. from an antenna, filter, duplexer,inductor, resistor or other upstream component). The combination of In+130 and In− 140 may be used to receive a differential input. Optionally,either of In+ 130 or In− 140 may be grounded to provide for a singleended input (into the ungrounded input). The output of LNA 100 is viaOut+ 150 and Out− 160. Out+ 150 is not inverted with respect to theinput signal In+ 130, and Out− 160 is not inverted with respect to theinput signal In− 140.

In some aspects, it may be advantageous to physically dispose certainelectrical components (e.g. Tune Block 172 and/or circuitry directedtoward pre-processing the signals for In+ 130 and/or In− 140) outsidePackage 102. In some embodiments, capacitors such as Capacitor 162, orany other capacitor in this description, may be optional.

FIG. 2 shows an embodiment having two bridges. LNA 200 includes LNA Core210, Bridge 170 and Bridge 270. LNA Core 210 includes FeedbackComponents 280. As with LNA 100, components of any bridge can be locatedon chip, on package, or outside of the package upon which the device ismounted. Similarly, any number of bridges can be incorporated intovarious embodiments.

Bridge 170 includes Tune Block 172, and Bridge 270 includes Tune Block272. Typically, Tune Block 272 tunes LNA 210 to a different frequencyband than Tune Block 172. By using both Bridge 170 and Bridge 270, LNA210 can be tuned to process signals in two separate bands (whileexcluding other bands). The tuned bands may correspond to the impedancesof Tune. Block 172 and Tune Block 272, respectively.

Any number of bridges can be incorporated into an LNA Core as desired.Two, four, eight or even twenty bridges can provide the ability to tuneto two, four, eight or twenty frequency bands, respectively, as desiredby the tuning requirements of the user. Alternately, shorting any bridge(i.e. setting the impedance of the relevant tune block equal to zero)provides for broadband amplification.

Implementations that have been designed for differential input may bemodified for use with single ended input sources if so desired, forexample by grounding the input that does not receive the single endedinput. For example, LNA 100 may be modified for single ended use bygrounding an input (e.g. In− 140). In some embodiments, the first gainstage can also function as a single ended to differential converter.

FIG. 3 is a more detailed block diagram of exemplary LNA Core 110. LNACore 110 includes BBV2V 300, which is a noninverting broadband voltageto voltage converter (in configurations where a tune block has zeroimpedance). LNA Core 110 also features two feedback circuits, FeedbackCircuit 310 and Feedback Circuit 320, along with additional FeedbackComponents 380. BBV2V 300 receives inputs In+ 130 and In− 140, andoutputs Out+ 150 and Out− 160. In this example, BBV2V 300 includesBridge 170, and a portion of Bridge 170 passes outside BBV2V 300, andother components of Bridge 170 are not shown.

In+ 130 is connected to Out− 160 via Feedback Circuit 310, whichincludes variable resistor Rf 312. In 140 is connected to Out+ 150 viaFeedback Circuit 320, which includes switchable resistor Rf 322. Each ofFeedback Circuits 310 and 320 can also include multiple resistors andthe circuitry to switch between these resistors. Incorporatingnonvariable resistors instead of variable resistors is also possible.Changing the resistance of the Feedback Circuits 310 and 320 along withchanges in Feedback Components 380 can be used to change the gain of LNA100 while keeping the impedance presented at In+ 130 and In− 140relatively constant. Because BBI2V 300 is noninverting, these exemplaryfeedback circuits connect each input to an output having oppositepolarity (i.e. a positive input is connected to a negative output).

This example of BBV2V 300 features three gain stages, connected inseries (connections not shown). Gm1 301 is the first gain stage, andreceives In+ 130 and In− 140. Gm1 301 electrically includes Bridge 170,although as previously described parts of Bridge 170 can physically passoutside of Gm1 301. The output of Gm1 301 is used as the input to Gm2302, the second gain stage. The output of Gm2 302 is used as the inputto Gm3 303. In this example, the output of Gm3 303 is Out+ 150 and Out−160.

Other embodiments provide for a Gm1 stage that receives single endedinput and outputs single ended output. In some of these cases, secondgain stages (e.g. a Gm2 stage) having a cross coupling circuit may beused as single ended to differential converters, providing differentialoutput to a third gain stage.

FIG. 3 also illustrates additional options where tuning can beimplemented (e.g. via the incorporation of Tune Block 172 and Capacitor162). FIG. 3 illustrates the incorporation of Tune Block 172 andCapacitor 162 into Feedback Circuits 310 and 320. In general, any of thefeedback circuits described herein (e.g. below) may be modified toinclude Tune Block 172 and/or Capacitor 162. As with other such examplesof incorporation, Tune Block 172 and/or Capacitor 162 may be located onthe chip upon which the device is fabricated, on the package upon whichthe device is packaged, off the package, or any other location. Thus inseveral embodiments, a portion of any circuit that provides for tuningmay be located in a physical region other than the region where thedevice being tuned is located. This decoupling between the physicallocation of certain components and the electrical connectivity of thesecomponents may provide for the convenient placement of particularlybulky components outside a chip or a package upon which a device isfabricated.

Even if Tune Block 172 and Capacitor 162 are not included in circuitssuch as Feedback Circuit 310, it may be advantageous to include a bypasscapacitor in this and other circuits that may appropriately block lowfrequencies. In general, the incorporation of a bypass capacitor orother basic electronic component in any circuit described herein isenvisioned, and the conditions under which such an incorporation isadvantageous are typically well known. As a result, bypass capacitorsand the like are often (though not always) omitted from variousschematics in order to improve clarity in the illustration.

FIG. 4 is a more detailed block diagram of exemplary LNA Core 210 ofFIG. 2. LNA Core 210 includes BBV2V 400, which is a noninvertingbroadband voltage to voltage converter. LNA Core 210 also features twofeedback circuits, Feedback Circuit 410 and Feedback Circuit 420, alongwith additional Feedback Components 480. BBV2V 400 receives inputs In+130 and In− 140, and outputs Out+ 150 and Out− 160. In this example,BBV2V 400 includes Bridge 170, and a portion of Bridge 170 passesoutside BBV2V 400. BBV2V 400 also includes Bridge 270, and a portion ofBridge 270 passes outside BBV2V 400.

In+ 130 is connected to Out− 160 via Feedback Circuit 410, which in thisexample includes switchable resister Rf 412. In− 140 is connected toOut+ 150 via Feedback Circuit 420, which in this example includesswitchable resistor Rf 422. Each of Feedback Circuits 410 and 420 canalso include multiple resistors and the circuitry to switch betweenthese resistors. Changing the resistance of Feedback Circuits 410 and420, while similarly changing the resistances within Feedback Components480, can be used to change the gain of LNA 200 while keeping theimpedance presented at In+ 130 and In− 140 relatively constant.Generally, the resistances of all feedback resistors may be eitherincreased or decreased together.

This example of BBV2V 400 features three gain stages, which can bedescribed as a combination of voltage to current converter (atransconductance element) followed by a current to voltage converter (atransimpedance element). Gm1 401 is the first gain stage, and receivesIn+ 130 and In− 140. Gm1 401 also includes Bridge 170 and Bridge 270.The output of Gm1 401 is used as the input to Gm2 302, the second gainstage. The output of Gm2 302 is used as the input to Gm3 303. In thisexample, the output of Gm3 303 is Out+ 150 and Out− 160.

Further LNA detail, particularly detail of the voltage to voltageconverter (e.g. BBV2V 300, BBV2V 400 or another broadband voltage tovoltage converter) will be described in the context of exemplary LNA 110and BBV2V 300. This simplification is for descriptive clarity only, andis not intended to limit the number of bridges that might be included orto limit any input tuning options.

FIG. 5 is a more detailed block diagram of BBV2V 300, the exemplarybroadband voltage to voltage converter of FIG. 3. BBV2V 300 includes Gm1301, Gm2 302 and Gm3 303, along with several feedback circuits. In thisexample, Gm1 301 is an inverting, common source transconductanceelement. Gm2 302 is a noninverting, common gate transconductanceelement, and Gm3 303 is an inverting, common source transconductanceelement that may be a push pull transconductance element in someembodiments.

Some aspects of BBV2V 300 can also be described as a voltage to currentconverter (i.e. Gm1 301) followed by a current to voltage converter (inthis example, the combination of Gm2 and Gm3), or alternately, as aninverting transconductance element in series with an invertingtransimpedance element.

Gm1 301 receives input signals In+ 130 and In− 140, and also includesBridge 170. The outputs of Gm1 301 are Out− 510 and Out+ 520, which areused as inputs to Gm2 302, with Out− 510 becoming In− 512, and Out+ 520becoming In+ 522. The outputs of Gm2 302 are Out− 514 and Out+ 524,which are used as inputs to Gm3 303, with Out− 514 becoming In− 516, andOut+ 524 becoming In+ 526. The outputs of Gm3 303 are Out+ 150 and Out−160.

This example of BBV2V 300 includes four feedback circuits wrappingaround Gm3 303 and both Gm2 302 and Gm3 303. Feedback Circuits 560, 564,570 and 574 include switchable resistors Rf 562, 566, 572 and 576,respectively. Feedback Circuits 560 and 574 connect inputs and outputsof the current to voltage converter (i.e. the combination of Gm2 302 andGm3 303). The combination of these two gain stages is inverting.Feedback circuits 564 and 570 connect the inputs and outputs of Gm3 303,which by itself is an inverting gain stage.

The combination of feedback circuits shown in FIG. 5 with feedbackcircuits shown in FIG. 3 creates a larger feedback circuit. Thisexemplary larger feedback circuit can be described as a group offeedback circuits, each connecting the output of the device to an inputof every transconductance element having opposite polarity. Thisfeedback circuit may create a broadband variable voltage gain acrossFeedback Circuits 310 and 320. In some embodiments, the resistances ofall resistors may be increased or decreased together in order to modifygain while maintaining impedance.

A variety of existing transconductance elements can be used to fabricateGm1 301, Gm2 302 and Gm3 303, and BBV2V 300 can be fabricated from feweror more transconductance elements. The following paragraphs describeseveral examples of new transconductance elements that may beparticularly useful when incorporated into an LNA such as LNA 100. Thesetransconductance elements and associated circuitry may also be useful inother applications (i.e. other than LNA 100, LNA 200 and the like), andLNA 100 can incorporate transconductance elements other than thosedescribed below. Unless otherwise specified, transistors having namesbeginning with “N” are n-type transistors, and transistors having namesbeginning with “P” are p-type transistors.

FIG. 6 is an example of one type of common source transconductanceelement appropriate for use in Gm1 301. One advantage of manytransconductance elements is the linearity of the gain from inputvoltages close to zero to very high input voltages. While high linearityover a broad range of input is desirable, it may also be desirable tomaintain high linearity for inputs near zero or near crossover. Manyexisting transconductance elements show a “kink” or other nonlinearityin their response near zero input, while several of the transconductanceelements described herein remain more linear near zero input. Someembodiments may display superior IIP3 (third order intercept point)behavior than existing transconductance or transimpedance elements, andin some implementations, IIP3 greater than 5 dBm may be achieved. Insome embodiments, transconductance elements use a combination of n-typeand p-type transistors for both positive and negative inputs. In otherembodiments, transconductance elements use a combination of pairs ofn-type and p-type transistors, arranged such that at least one n-typeand one p-type transistor combine to provide transconductance even aspolarity of the input signal changes. Thus for the purposes of thisspecification, a linear transconductance element has a particularly highlinearity (relative to existing transconductance elements) in the regimeclose to zero input voltage. In some embodiments, this linearity isachieved by combining the functionality of both n-type and p-typetransistors on both positive and negative input polarities.

CSLTE 600 is a common source linear transconductance element, powered byPower Supply 690 via NLoad 630, and grounded to Ground 692 via PLoad632. CLSTE 600 receives inputs In+ 130 and In− 140, and outputs Out− 510and Out+ 520. CLSTE 600 includes n-type transistors N1 610 and N2 620,and also includes p-type transistors P1 612 and P2 622. The transistorsare paired as shown, with the sources of N1 610 and P1 612 connected,and the sources of N2 620 and P2 622 connected. The drains for N1 610and N2 620 connect to NLoad 630, and the drains for P1 612 and P2 622connect to PLoad 632. Certain embodiments of linear transconductanceelements such as CSLTE 600 may not require a current source.

The sources are connected as shown by Bridge 170. In this example,Bridge 170 is contained on the chip upon which CLSTE 600 is fabricated.Bridge 170 includes two capacitors, Capacitor 174 and Capacitor 176; inthis example, Bridge 170 does not include an inductor or other impedancecircuit. As with capacitors in general, Capacitor 174 and Capacitor 176function as high pass filters.

In this example, DC bias to the transistor gates is provided by biascircuits. Input voltages from these bias circuits are received at BiasN1640, BiasN2 650, BiasP1 642 and BiasP2 652, which provide DC bias thegates of transistors N1 610, N2 620, P1 612 and P2 622, respectively.

The bias inputs are connected to the input signals as shown. In+ 130connects to BiasN1 640 via capacitor N1Cap 670. In+ 130 connects toBiasP1 642 via capacitor P1Cap 672. In− 140 connects to BiasN2 650 viacapacitor N2Cap 680, and In− 140 connects to BiasP2 652 via capacitorP2Cap 682.

The outputs are connected to the drains as shown. Out− 510 is connectedto the drain of N1 610, and is also connected to the drain of P1 612 viacapacitor OutCap 660. Out+ 520 is connected to the drain of N2 620, andis also connected to the drain of P2 622 via capacitor OutCap 662.

NLoad 630 and PLoad 632 provide for the passage of current to/from theirrespective transistors from the power supply and ground, respectively.NLoad 630 and PLoad 632 are not current limiting. However, they alsopresent high resistance to current flow relative to the resistancepresented by outputs Out+ 520 and Out− 510. NLoad 630 and PLoad 632 canbe resistive loads (e.g. resistors) or active loads (e.g. a part of thecircuitry described in FIG. 26 below).

Capacitor 174 and Capacitor 176 can optionally be replaced with banks ofseveral capacitors and the circuitry to switch between them in order toprovide adjustable capacitance. In some embodiments, it may beadvantageous to adjust the capacitance of Bridge 170 to change thecenter frequency of the band passed by Bridge 170.

Bridge 170 may provide an important function other than tuning to aspecific band (which in this example of a broadband circuit, is notprovided for). In some embodiments, the voltage at the junction betweenpairs of transistors in series (e.g. the voltage at the joined sourcesof N1 610 and P1 612, or the voltage at the joined sources of N2 620 orP2 622) is not fixed, and may fluctuate according. In some embodiments,this fluctuation may be associated with input signals, and in somecases, these fluctuations may induce a current flow in Bridge 170 fromone pair of sources to the other pair of sources (in either direction).If Bridge 170 includes an impedance circuit, this current flow can beenabled only for frequencies passed by the circuit. If Bridge 170 isshorted, this current flow can be enabled for all frequencies. Thus, forfrequencies passed by Capacitors 174 and 176, Bridge 170 allows currentflow between the sources of N1 610/P1 612 and the sources of N2 620/P2622 without constraining the voltage at either of these junctions. Forembodiments that feature a single pair of transistors, Bridge 170 canalso be connected to ground at the end opposite the end connected to thepair of transistors.

An aspect of CSLTE 600 is that A/C voltage may be converted to A/Ccurrent using both n-type and p-type transistors for both positive andnegative voltage. As In+ 130 increases (and In− 140 decreases), currentmay be increasingly carried by the combination of N1 610 and P2 622. AsIn+ 130 decreases (and In− 140 increases), current may be increasinglycarried by the combination of N2 620 and P1 612. Whereas many existingtransconductance elements display a “kink” in the I-V response near zeroinput voltage, CSLTE 600 may not. As a result, the linearity of CSLTE600 may be improved, and CSLTE 600 is thus called a “linear” commonsource transconductance element for the purposes of this specification.

FIGS. 7A, 7B and 7C show several options for bridge configurations.These examples are illustrative, and are not intended to be limiting.The choice of number and configuration of bridges is one of the majordifferences between (e.g.) LNA 100 and LNA 200.

FIG. 7A shows the bridge used for CSLTE 600, and is provided as areference. Because Tune Block 172 has zero impedance in this example(and so functions as a simple connection between Capacitor 174 andCapacitor 176) it is not shown. An LNA incorporating this configurationof Bridge 170 would provide broadband amplification.

FIG. 7B shows two bridges, Bridge 170 and Bridge 270. Bridge 170includes Tune Block 172, and Bridge 270 includes Tune Block 272. Bridge170 includes Capacitor 174 and Capacitor 176 on either side of TuneBlock 172, and Bridge 270 includes Capacitor 274 and Capacitor 276 oneither side of Tune Block 272. In each bridge, the combination ofcapacitors and tune block (which has an impedance) creates a bandpassfilter. Because shorting either of Tune Block 172 or Tune Block 272(i.e. reducing the impedance of either tune block to zero) provides forbroadband amplification, the incorporation of multiple bridges typicallyincludes the incorporation of tune blocks that have appreciableimpedances, i.e. are not shorted.

In some cases, it may be convenient to include an inductor as part of atune block in order to provide impedance. It may also be convenient toplace this inductor outside of the chip upon which the bridge isfabricated. In this example, Pads 120 are used to schematically showthat a portion of each bridge that includes the tune block can be offchip, off package, or otherwise separate from the chip upon which thebridge is fabricated. Thus, either or both of Tune Blocks 172 and 272can be off chip if so desired. Alternately, Tune Block 172 and/or TuneBlock 272 could be fabricated on chip if so desired, and any ofcapacitors Capacitor 174, Capacitor 176, Capacitor 274 and Capacitor 276could be fabricated on or off chip if so desired.

By using an appropriate impedance (e.g via tune blocks) and capacitance(via capacitors), Bridge 270 can be designed to pass a differentfrequency band than the band passed by Bridge 170. Because these bridgesare connected in parallel to the sources of the respective transistors,either may allow for current passage as previously described. Thus, atransconductance device (such as CSLTE 600) that incorporates multiplebridges can be tuned to amplify multiple desired bands while excludingother frequencies.

Additional bridges can be added as desired, providing for additionalpassed bands. FIG. 7C adds an additional Bridge 370 to the previouslydescribed pair of Bridge 170 and Bridge 270. Bridge 370 includescapacitors Capacitor 374 and Capacitor 376 in series with Tune Block372. By choosing the capacitance of Capacitor 374 and Capacitor 376 andthe impedance of Tune Block 372 appropriately, a device incorporatingBridge 170, Bridge 270 and Bridge 370 as shown can amplify threediscrete bands. If further bands are desired, additional bridges can besimilarly added. These tuning techniques can be applied totransconductance elements other than CSLTE 600.

FIG. 8 shows another common source transconductance element CSTE 800.CSTE 800 is powered by Power Supply 690 and grounded by Ground 692.Current to one side of the circuit is supplied by ISource 891, andcurrent to the other side of the circuit is supplied by ISource 892. Thecircuit includes Capacitor 861, Capacitor 862, Capacitor 863 andCapacitor 864, connected by Tune Block 872 as shown. Tune Block 872 canhave an impedance (for tuned amplification) or can be shorted.

The input signal at In− 140 is copied to the gates of both p-typetransistor P2 822 and n-type transistor N2 820. The input signal at In−140 is also transmitted through Resistor 881 to connect as shown to Out+520. This connection also connects the drains of P2 822 and N2 820 toOut+ 520 and Resistor 881 as shown. The source of N2 820 connects toCapacitor 863 to Resistor 883. Resistor 883 connects to Ground 692 asshown. The source of P2 822 connects to ISource 892 and Capacitor 862 asshown.

Similarly, the input signal at In+ 130 is copied to the gates oftransistors P1 812 and N1 810. The input signal at In+ 130 is alsotransmitted through Resistor 880 to connect as shown to Out− 510. Thisconnection also connects the drains of P1 812 and N1 810 to Out− 510 andResistor 880 as shown. The source of N1 810 connects to Capacitor 864and Resistor 882. Resistor 882 also connects to Ground 692 as shown. Thesource of P1 812 connects to the wire connecting ISource 891 toCapacitor 861 as shown.

CSTE 800 can be used as either a differential transconductance elementor a single ended transconductance element. For use with a single endedinput, the other input may be grounded.

FIG. 9 shows another embodiment of a common source transconductanceelement, CSTE 900. Like CSTE 800, CSTE 900 may feature good supplyrejection and ground rejection, but CSTE 900 may provide additionalheadroom. CSTE 900 is powered by Power Supply 690 and grounds to Ground692. Current to one side of the circuit is supplied by ISource 991, andcurrent to the other side of the circuit is supplied by ISource 992. Thecircuit includes Capacitor 961, Capacitor 962, Capacitor 963 andCapacitor 964, connected to Tune Block 972 as shown. Tune Block 972 canhave an impedance (for tuned amplification) or can be shorted.

The input signal at In+ 130 is fed to the gates of transistors P1 912and N1 910. The input signal at In+ 130 is also transmitted throughResistor 980 to connect to Out− 510. The signal at Out 510 also connectsthe drains of P1 912 and N1 910 to Out− 510 and Resistor 980. The sourceof N1 910 connects to the wire connecting Capacitor 964 to the drain oftransistor N3 930. Resistor 982 connects the drains of P1 912 and N1 910to both Capacitor 966 and the gate of transistor N3 930. The source ofN3 930 connects to both Ground 692 and the end of Capacitor 966 oppositethe end connected to the gate of N3 930 as shown. The source of P1 912connects to the wire connecting ISource 991 to Capacitor 961 as shown.

The input signal at In− 140 is fed to the gates of transistors P2 922and N2 920. The input signal at In− 140 is also transmitted throughResistor 981 to Out+ 520. This connection also connects the drains of P2922 and N2 920 to Out+ 520 and Resistor 981. The source of N2 920connects to the wire connecting Capacitor 963 to the drain of transistorN4 940. Resistor 983 connects the drains of P2 922 and N2 920 to bothCapacitor 965 and the gate of transistor N4 940. The source of N4 940connects to both Ground 692 and the end of Capacitor 965 opposite theend connected to the gate of N4 940 as shown. The source of P2 922connects to the wire connecting ISource 992 to Capacitor 962.

FIG. 10 shows yet another example of a common source transconductanceelement. In some embodiments, this version may have even better headroomthan the element shown in FIG. 9. CSTE 1000 is powered by Power Supply690 and grounds to Ground 692. Current to one side of the circuit issupplied by ISource 1091, and current to the other side of the circuitis supplied by ISource 1092. The connections to Bridge 170 are shown,but the components of Bridge 170 are omitted for clarity.

In this embodiment, CSTE 1000 has only n-type transistors. In + 130receives an input signal, and is connected to the gate of transistor N11010. In+ 130 is also connected to resistor 1080, which connects In+ 130to the wire connecting ISource 1091 to the drain of N1 1010. The drainof N1 1010 is also connected to output Out− 510 and one side of Resistor1082. The other side of Resistor 1082 connects to Capacitor 1060, whichthen connects to Ground 692. The source of N1 1010 is connected to thedrain of transistor N2 1015. One leg of Bridge 170 connects at thisjunction between the source of N1 1010 and drain of N2 1015. The sourceof N2 1015 connects to Ground 692, and the gate of N2 1015 is connectedto the wire connecting Resistor 1082 to Capacitor 1060.

In− 140 receives an input signal, and is connected to the gate oftransistor N3 1020. Also connected to In− 140 is Resistor 1083, whichconnects In− 140 to the wire connecting ISource 1092 to the drain of N31020. The drain of N3 1020 is also connected to output Out+ 520 and oneside of Resistor 1081. The other side of Resistor 1081 connects toCapacitor 1062, which then connects to Ground 692. The source of N3 1020is connected to the drain of transistor N4 1025. The other leg of Bridge170 connects at this junction between the source of N3 1020 and drain ofN4 1025. The source of N4 1025 connects to Ground 692, and the gate ofN4 1025 is connected to the wire connecting Resistor 1081 to Capacitor1062. CSTE 1000 may be used with a single ended input by grounding theother input.

The following several figures show different embodiments of biascircuits for creating a DC gate bias for one or more transistors. Anexemplary transconductance element that requires a bias circuit is CSLTE600. Thus, the bias circuits in the following figures provide the biasinputs into other circuits (e.g. CSLTE 600).

FIG. 11 is a schematic diagram of exemplary Bias Circuit 1100. BiasCircuit 1100 is powered by Power Supply 1190 and is grounded by Ground1192. Bias voltage from Bias Circuit 1100 is output to the respectivetransistors whose gates are being biased by Bias Circuit 1100 at outputsBiasN1 640, BiasN2 650, BiasP1 642 and BiasP2 652. Current is sourced byISource 1191, which connects to Power Supply 1190.

Bias Circuit 1100 includes two transistors, n-type transistor N3 1130and p-type transistor P3 1132. N3 1130 and P3 1132 are connected attheir sources as shown. The gate of N3 1130 is connected to the drain ofN3 1130, and the gate of P3 1132 is connected to the drain of P3 1132.The drain of N3 1130 is connected to Isource 1191, and is alsoconnected/to Resistor 1183 and Resistor 1180. Resistor 1183 connects thedrain of N3 1130 to BiasN1 640, and Resistor 1180 connects the drain ofN3 1130 to BiasN2 650. The drain of P3 1132 is connected to Resistor1184, whose other end connects to Ground 1192 as shown. The drain of P31132 is also connected to Resistor 1182 and Resistor 1181. Resistor 1182connects the drain of P3 1132 to BiasP1 642, and Resistor 1181 connectsthe drain of P3 1132 to BiasP2 652.

FIG. 12 is a schematic of Bias Circuit 1200, which includes the samecomponents as Bias Circuit 1100, in a similar configuration, but withthe positions of current source ISource 1191 and Resistor 1184 reversed.Thus, Resistor 1184 connects Power Supply 1190 to the rest of thecircuit, and the circuit is connected to Ground 1192 via current sourceISource 1191.

FIG. 13 is a schematic of exemplary Bias Circuit 1300, which is poweredby Power Supply 1390 and is grounded by Ground 1392. Bias voltage fromBias Circuit 1300 is output to the respective transistors whose gatesare being biased by Bias Circuit 1300 at outputs BiasN1 640, BiasN2 650,BiasP1 642 and BiasP2 652. Current is sourced from ISource 1391, whichconnects to Ground 1392. Power Supply 1390 connects to both one side ofCapacitor 1372 and the source of p-type transistor P1 1312. The gate ofP1 1312 connects to the other side of Capacitor 1372. This junctionbetween Capacitor 1372 and the wire to the gate of P1 1312 is alsoconnected to Resistor 1384, which then connects to the sources oftransistors N1 1310 (n-type) and P2 1322 (p-type); these sources areconnected to each other.

The drain of P1 1312 connects to the drain of N1 1310. The drain andgate of N1 1310 are also connected. The drain of N1 1310 connects toResistor 1383, which then connects to output BiasN1 640. The drain of N11310 also connects to Resistor 1380, which then connects to outputBiasN2 650.

The drain and gate of P2 1322 are connected. The drain of P2 1322 alsoconnects to ISource 1391, which then connects to Ground 1392. The drainof P2 1322 is also connected to Resistor 1382, which then connects tooutput BiasP1 642. The drain of P2 1322 is also connected to Resistor1381, which then connects to output BiasP2 652.

FIG. 13 also shows an embodiment of a wrapping circuit. Wrapping Circuit1399 comprises transistor P1 1312, Capacitor 1372 and Resistor 1384.Other embodiments may be constructed with n-type transistors also. Thisembodiment of Wrapping Circuit 1399 has two points of connection thatconnect (i.e. “wrap”) around a device being wrapped. A wrapping circuitconnects to an electronic device on two sides (i.e. at two connectionsto the device), and typically makes a connection from the device toeither a ground or a power supply. A wrapping circuit may create a highimpedance connection between the device (being wrapped) and a ground,power supply or similar component. A wrapping circuit may also protectthe device (being wrapped) from ground noise and/or supply noise.Wrapping circuits can be used in a wide variety of circuits, andexamples are shown in FIGS. 9, 10, 14, 18 and 19 (although the wrappingcircuits are not independently defined so as to improve clarity of theseillustrations). In FIG. 13, Wrapping Circuit 1399 wraps N1 1310, byconnecting to both the drain of N1 1310 and the gate of N1 1310.

FIG. 14 is a schematic diagram of another exemplary Bias Circuit 1400,which is powered by Power Supply 1490 and is grounded by Ground 1492.Bias voltage from Bias Circuit 1400 is output to the respectivetransistors whose gates are being biased by Bias Circuit 1400 at outputsBiasN1 640, BiasN2 650, BiasP1 642 and BiasP2 652. Current is sourcedfrom ISource 1491, which connects to Power Supply 1490.

ISource 1491 also connects to the drain and gate of n-type transistor N11410. The drain of N1 1410 also connects to Resistor 1483, which thenconnects to output BiasN1 640. The drain of N1 1410 also connects toResistor 1480, which then connects to BiasN2 650. The source of N1 1410is connected to the source of p-type transistor P1 1412. Both of thesesources are connected to Resistor 1484, which then connects to Capacitor660, which then connects to Ground 1492. The gate and drain of P1 1412are connected. The drain of P1 1412 also connects to Resistor 1482,which then connects to output BiasP1 642. The drain of P1 1412 alsoconnects to Resistor 1481, which then connects to output BiasP2 652. Thedrain of P1 1412 also connects to the drain of n-type transistor N21420. The source of N2 1420 connects to Ground 1492. The gate of N2 1420is connected to the junction between Resistor 1484 and Capacitor 660.

Bias circuit 1400 also includes a wrapping circuit, comprised of N21420, Capacitor 660 and Resistor 1481, wrapping around P1 1412.

FIG. 15 is an exemplary common gate transconductance element,appropriate for use in Gm2 302. Gm2 1500 is a cross coupled, commongate, linear transconductance element. Gm2 1500 is powered by PowerSupply 1590 via NLoad 1530 and is grounded via PLoad 1532 to Ground1592. In some embodiments, cross coupling can provide for noisecancellation. In other embodiments, cross coupling can provide for theconversion of a single ended input into a differential output.

Gm2 1500 receives inputs In− 512 and In+ 522, and outputs Out− 514 andOut+ 524. Gm2 1500 includes four transistors: n-type transistors N1 1510and N2 1520, and p-type transistors P1 1512 and P2 1522.

The drain of N1 1510 is connected to NLoad 1530. The drain of N1 1510 isalso connected to Capacitor 1561, which then connects to Out− 514. Thedrain of P1 1512 is connected to PLoad 1532. The drain of P1 1512 isalso connected to Capacitor 1567, which then connects to Out− 514. Thus,the drains of N1 1510 and P1 1512 are connected by Capacitor 1561 andCapacitor 1567 in series.

The gate of N1 1510 is biased by input from BiasN1 640. The gate of P11512 is biased by input from BiasP1 642. These two inputs (and the gatesof N1 1510 and P1 1512) are connected by Capacitor 1560 and Capacitor1568 in series. Capacitors 1560 and 1568 are connected to the sources ofN2 1520 and P2 1522 by Coupling 1554.

The sources of N1 1510 and P1 1512 are connected. These sources are alsoconnected to Capacitor 1569, which then connects to In− 512.

The drain of N2 1520 is connected to NLoad 1530. The drain of N2 1520 isalso connected to Capacitor 1562, which then connects to Out+ 524. Thedrain of P2 1522 is connected to PLoad 1532. The drain of P2 1522 isalso connected to Capacitor 1566, which then connects to Out+ 524. Thus,the drains of N2 1520 and P2 1522 are connected by Capacitor 1562 andCapacitor 1566 in series.

The gate of N2 1520 is biased by input from BiasN2 650. The gate of P21522 is biased by input from BiasP2 652. These two inputs (and the gatesof N2 1520 and P2 1522) are connected by Capacitor 1563 and Capacitor1565 in series. Capacitors 1563 and 1565 are connected to the sources ofN1 1510 and P1 1512 by Coupling 1555.

In this example, Coupling 1554 connects the side of Capacitor 1560opposite the gate of N1 1510 to the sources of N2 1520 and P2 1522.Similarly, Coupling 1555 connects the side of Capacitor 1565 oppositethe gate of P2 1522 to the sources of N1 1510 and P1 1512. Thecombination of Coupling 1554 and Capacitors 1560 and 1568 creates anexemplary coupling circuit. The combination of Capacitors 1565 and 1563with Coupling 1555 also creates an exemplary coupling circuit. Thecombination of these two coupling circuits creates a cross coupling, andso Gm2 1500 is an example of a cross coupled transconductance element. Akey feature of this embodiment is that the gates on one side of thecircuit are connected to the sources on the opposite side of thecircuit. This cross coupled transconductance element has severalfeatures. When operated in a differential mode (i.e. receivingdifferential input), the cross coupling can provide noise cancellation,and in some cases can convert differential or gate noise at the inputsto common mode noise at the outputs. In cases where Gm2 1500 is beingadapted for use with single ended input, the cross coupling circuit canprovide for the conversion of single ended input into differentialoutput. In some aspects, the cross coupling converts single ended inputto differential output can be thought of as the formation of twocircuits: a common gate transconductance element that converts currentto voltage with positive polarity, and a common source voltage tovoltage converter with negative polarity, with both circuits havingsimilar gain. Thus, cross coupled transconductance elements such as Gm21500 can function as single ended to differential converters.

The sources of N2 1520 and P2 1522 are connected. These sources are alsoconnected to Capacitor 1564, which then connects to In+ 522.

NLoad 1530 and PLoad 1532 provide for the passage of current, and arenot current limiting. They also present high resistance to current flowrelative to the resistance presented by outputs Out+ 520 and Out− 510.NLoad 1530 and PLoad 1532 can be resistive loads or active loads.

FIG. 16 is an exemplary common gate transconductance element,appropriate for use in Gm2 302. Gm2 1600 is a cross coupled, common gatelinear transconductance element that is self biasing. Gm2 1600 ispowered by Power Supply 1690 via NLoad 1630 and is grounded via PLoad1632 to Ground 1692. Gm2 1600 features cross coupling as did Gm2 1500.

Gm2 1600 receives inputs In− 512 and In+ 522, and outputs Out− 514 andOut+ 524. Gm2 1600 includes four transistors: n-type transistors N1 1610and N2 1620, and p-type transistors P1 1612 and P2 1622.

NLoad 1630 is connected to the drain of N1 1610. The drain of N1 1610 isalso connected to Capacitor 1661, which then connects to output Out−514. The drain of N1 1610 is connected to the gate of N1 1610 throughresistor 1680. The gate of N1 1610 is also connected to Capacitor 1660,which then connects to the sources of N2 1620 and P2 1622. The sourcesof N1 1610 and P1 1612 are connected. Capacitor 1668 also connects tothese sources, and the side of Capacitor 1668 opposite the sources isconnected to In− 512.

PLoad 1632 is connected to the drain of P1 1612. The drain of P1 1612 isalso connected to Capacitor 1666, which then connects to output Out−514. The drain of P1 1612 is connected to the gate of P1 1612 throughResistor 1683. The gate of P1 1612 is also connected to Capacitor 1667,which then connects to the sources of N2 1620 and P2 1622.

The side of Capacitor 1660 opposite Resistor 1680 also connects to theside of Capacitor 1667 opposite Resistor 1683.

NLoad 1630 is connected to the drain of N2 1620. The drain of N2 1620 isalso connected to Capacitor 1662, which then connects to output Out+524. The drain of N2 1620 is connected to the gate of N2 1620 throughresistor 1681. The gate of N2 1620 is also connected to Capacitor 1663,which then connects to the sources of N1 1610 and P1 1612. The sourcesof N2 1620 and P2 1622 are connected. Capacitor 1669 also connects tothese sources, and the side of Capacitor 1669 opposite the sources isconnected to In+ 522.

PLoad 1632 is connected to the drain of P2 1622. The drain of P2 1622 isalso connected to Capacitor 1665, which then connects to output Out+524. The drain of P2 1622 is connected to the gate of P2 1622 throughResistor 1682. The gate of P2 1622 is also connected to Capacitor 1664,which then connects to the sources of N1 1610 and P1 1612.

The side of Capacitor 1663 opposite Resistor 1681 also connects to theside of Capacitor 1664 opposite Resistor 1682.

In this example, Coupling 1554 connects the side of Capacitor 1660opposite the gate of N1 1610 to the sources of N2 1620 and P2 1622.Similarly, Coupling 1555 connects the side of Capacitor 1664 oppositethe gate of P2 1622 to the sources of N1 1610 and P1 1612. Thecombination of Coupling 1554 and Capacitors 1660 and 1667 creates anexemplary coupling circuit. The combination of Capacitors 1663 and 1664with Coupling 1555 also creates an exemplary coupling circuit. Thecombination of these two coupling circuits creates a cross coupling, andso Gm2 1600 is an example of a cross coupled transconductance element. Akey feature of this embodiment is that the gates on one side of thecircuit are connected to the sources on the opposite side of thecircuit.

FIG. 17 is another exemplary common gate transconductance element,appropriate for use in Gm2 302. Gm2 1700 is a common gatetransconductance element.

Gm2 1700 is powered by Power Supply 1790 and grounds to Ground 1792.Current is supplied by current sources ISource 1791 and ISource 1793.Gm2 1700 receives inputs In− 512 and In+ 522, and outputs Out− 514 andOut+ 524. Gm2 1700 includes six transistors: n-type transistors N1 1710,N2 1720, N3 1730, and N4 1740, along with p-type transistors P1 1712 andP2 1722.

ISource 1791 connects to the source of P1 1712. The source of P1 1712 isalso connected to Capacitor 1760, which then connects to In− 512. In−512 also connects to Capacitor 1765, which then connects to the sourceof N1 1710 and drain of N3 1730. The drain of P1 1712 connects to thedrain of N1 1710. These drains are also connected to Out− 514. Thesedrains and Out− 514 are also connected to Resistor 1780, which thenconnects to Capacitor 1766. The connection between Resistor 1780 andCapacitor 1766 is also connected to the gate of P1 1712 and the gate ofN1 1710, hence these gates are connected. The side of Capacitor 1766opposite the gate connections is connected to Ground 1792.

The source of N1 1710 is connected to drain of N3 1730. The source of N31730 is connected to Ground 1792. The gate of N3 1730 is connected tothe gate of N4 1740. These gates are also connected to Capacitor 1764,which then connects to Ground 1792.

The drains of P1 1712 and N1 1710 are connected to Resistor 1783, whichthen connects to Resistor 1782. Resistor 1782 then connects to thedrains of P2 1722 and N2 1720.

ISource 1793 connects to the source of P2 1722. The source of P2 1722 isalso connected to Capacitor 1761, which then connects to In+ 522. In+522 also connects to Capacitor 1763, which then connects to the sourceof N2 1720 and drain of N4 1740. The drain of P2 1722 connects to thedrain of N2 1720. These drains are also connected to Out+ 524. Thesedrains and Out+ 524 are also connected to Resistor 1781, which thenconnects to Capacitor 1762. The connection between Resistor 1781 andCapacitor 1762 is also connected to the gate of P2 1722 and the gate ofN2 1720, hence these gates are connected. The side of Capacitor 1762opposite the gate connections is connected to Ground 1792.

The source of N2 1720 is connected to the drain of N4 1740. The sourceof N4 1740 is connected to Ground 1792. The gate of N4 1740 is connectedto the gate of N3 1730. These gates are also connected to Capacitor1764, which then connects to Ground 1792.

The drains of P2 1722 and N2 1720 are connected to Resistor 1782, whichthen connects to Resistor 1783. Resistor 1783 then connects to thedrains of P1 1712 and N1 1710. The connection between Resistors 1782 and1783 is connected to the gates of N3 1730 and N4 1740.

FIG. 18 is another exemplary common gate transconductance element,appropriate for use in Gm2 302. Gm2 1800 is a common gatetransconductance element.

Gm2 1800 is powered by Power Supply 1890 and grounds to Ground 1892.Current is supplied by current sources ISource 1891 and ISource 1893.Gm2 1800 receives inputs In− 512 and In+ 522, and outputs Out− 514 andOut+ 524. Gm2 1800 includes six transistors: n-type transistors N1 1810,N2 1820, N3 1830, and N4 1840, along with p-type transistors P1 1812 andP2 1822.

ISource 1891 connects to the source of P1 1812. The source of P1 1812 isalso connected to Capacitor 1860, which then connects to In− 512. In−512 also connects to Capacitor 1865, which then connects to the sourceof N1 1810 and drain of N3 1830. The drain of P1 1812 connects to thedrain of N1 1810. These drains are also connected to Out− 514. Thesedrains and Out− 514 are also connected to Resistor 1880, which thenconnects to Capacitor 1866. The connection between Resistor 1880 andCapacitor 1866 is also connected to the gate of P1 1812 and the gate ofN1 1810, hence these gates are connected. The side of Capacitor 1866opposite the connection to Resistor 1880 connects to the gates of P21822 and N2 1820.

The source of N1 1810 is connected to the drain of N3 1830. The sourceof N3 1830 is connected to Ground 1792. The gate of N3 1830 is connectedto the gate of N4 1840. These gates are also connected to Capacitor1864, which then connects to Ground 1792.

The drains of P1 1812 and N1 1810 are connected to Resistor 1883, whichthen connects to Resistor 1882. Resistor 1882 then connects to thedrains of P2 1822 and N2 1820.

ISource 1893 connects to the source of P2 1822. The source of P2 1822 isalso connected to Capacitor 1861, which then connects to In+ 522. In+522 also connects to Capacitor 1863, which then connects to the sourceof N2 1820 and drain of N4 1840. The drain of P2 1822 connects to thedrain of N2 1820. These drains are also connected to Out+ 524. Thesedrains and Out+ 524 are also connected to Resistor 1881, which thenconnects to Capacitor 1866. The connection between Resistor 1881 andCapacitor 1866 is also connected to the gate of P2 1822 and the gate ofN2 1820, hence these gates are connected. The side of Capacitor 1866opposite the connection to Resistor 1881 connects to the gates of P11812 and N1 1810.

The source of N2 1820 is connected to the drain of N4 1840. The sourceof N4 1840 is connected to Ground 1892. The gate of N4 1840 is connectedto the gate of N3 1830. These gates are also connected to Capacitor1864, which then connects to Ground 1892.

The drains of P2 1822 and N2 1820 are connected to Resistor 1882, whichthen connects to Resistor 1883. Resistor 1883 then connects to thedrains of P1 1812 and N1 1810. The connection between Resistors 1882 and1883 is connected to the gates of N3 1830 and N4 1840.

Gm2 1800 also includes two exemplary wrapping circuits. N1 1810 iswrapped by the wrapping circuit comprising N3 1830, Capacitor 1864, andResistor 1883. N2 1820 is wrapped by the wrapping circuit comprising N41840, Capacitor 1864 and Resistor 1882.

FIG. 19 shows another exemplary common gate transconductance element,appropriate for use in Gm2 302. Gm2 1900 is a cross coupled, common gatetransconductance element. Many features of Gm2 1900 are similar to thoseof Gm2 1800. However Gm2 1900 has two additional circuits, and Gm2 1900does not have the circuit comprising Capacitor 1866 that is present inGm2 1800. The gates of P1 1812 and N1 1910 are connected to Capacitor1967, which then connects to In+ 522. The gates of P2 1822 and N2 1820are connected to Capacitor 1962, which then connects to In− 512. Thecircuits including Capacitors 1962 and 1967 substantially form a crosscoupling circuit.

In this example, Coupling 1554 connects the side of Capacitor 1967opposite the gates of N1 1810 and P1 1812 to the sources of N2 1620 andP2 1622. Similarly, Coupling 1555 connects the side of Capacitor 1664opposite the gate of P2 1622 to the sources of N1 1610 and P1 1612. Thecombination of Coupling 1554 and Capacitors 1660 and 1667 creates anexemplary coupling circuit. The combination of Capacitors 1663 and 1664with Coupling 1555 also creates an exemplary coupling circuit. Thecombination of these two coupling circuits creates a cross coupling, andso Gm2 1600 is an example of a cross coupled transconductance element. Akey feature of this embodiment is that the gates on one side of thecircuit are connected to the sources on the opposite side of thecircuit.

FIG. 20 is an exemplary push pull transconductance element appropriatefor use in Gm3 303. Gm3 2000 is a common source, push pulltransconductance element, and is powered by Power Supply 2090 and isgrounded by Ground 2092. Gm3 2000 receives inputs In− 516 and In+ 526,and outputs Out+ 150 and Out− 160. The output signals are inverted withrespect to the input signals. Gm3 2000 includes n-type transistors N12010, N2 2020 and N3 2030. Gm3 2000 also includes p-type transistors P12012, P2 2022 and P3 2032. In this example transconductance element, anexample of a bias circuit (including P1 2012 and N1 2010) is includedwith other transconductance circuitry on the same diagram.

Power Supply 2090 connects to the source of P1 2012. Power Supply 2090also connects to Capacitor 2060, which then connects to the gate of P12012. The gate of P1 2012 is also connected to Resistor 2080, which thenconnects to the drain of P1 2012. The drain of P1 2012 connects toResistor 2081, which then connects to the drain of N1 2010.

Ground 2092 connects to the source of N1 2010. Ground 2092 also connectsto Capacitor 2063, which then connects to the gate of N1 2010. The gateof N1 2010 also connects to Resistor 2082, which then connects to thedrain of N1 2010.

The drain of P1 2012 is connected to the gate of P2 2022 via Resistor2084, providing gate bias. The drain of P1 2012 is also connected to thegate of P3 2032 via Resistor 2083, providing gate bias. The drain of N12010 is connected to the gate of N2 2020 via resistor 2085, providinggate bias. The drain of N1 2010 is connected to the gate of N3 2030 viaResistor 2086, providing gate bias. The gate of P3 2032 is connected toCapacitor 2064, which is then connected to In− 516. The gate of P2 2022is connected to Capacitor 2061, which then connects to In+ 526. The gateof N3 2030 is connected to Capacitor 2065, which is then connected toIn− 516. The gate of N2 2020 is connected to Capacitor 2062, which isthen connected to In+ 526.

The sources of P3 2032 and P2 2022 are connected to Power Supply 2090.The sources of N3 2030 and N2 2020 are connected to Ground 2092. Thedrain of P3 2032 is connected to the drain of N3 2030, and these drainsconnect to Out+ 150. The drain of P2 2022 is connected to the drain ofN2 2020, and these drains connect to Out− 160.

FIG. 21 is a schematic of an exemplary LNA Core that also includes abuffer stage and nested feedback circuits. Buffered LNA Core 2110features a single Bridge 170, and both the broadband voltage to voltageconverter and the feedback components are shown in the same figure. Thefirst three gain stages, Gm1 301, Gm2 302 and Gm3 303 are similar tothose of BBV2V 300 and LNA Core 110. However, Buffered LNA Core 2110takes the output of Gm3 303 to an input for a buffer stage, Buffer 2104.Additionally, the feedback components of Buffered LNA Core 2110 aredifferent from those of LNA Core 110 and BBV2V 300.

Out+ 150 of Gm3 303 is connected to In+ 2130 of the buffer stage Buffer2104. Out− 160 of Gm3 303 is connected to In− 2140 of Buffer 2104. Theoutputs of Buffer 2104, Out+ 2132 and Out− 2142, are connected to theoutputs of the device, Out+ 2150 and Out− 2160, respectively.

Several nested feedback circuits connect different inputs and outputs asshown. To simplify the diagram, each feedback circuit is annotated bythe resistor included in this circuit. Switchable resistor Rf 2180provides feedback between In+ 130 and Out− 2160. Resistor Rf 2181provides feedback between In+ 130 and In− 2140 (which is connected toOut− 160). Switchable resistor Rf 2182 provides feedback between Out−510 and Out+ 2150. Resistor Rf 2183 provides feedback between Out− 510and In+ 2130. Switchable resistor Rf 2184 provides feedback between Out−514 and Out+ 2150. Resistor Rf 2185 provides feedback between Out− 514and Out+ 150.

Switchable resistor Rf 2190 provides feedback between In− 140 and Out+2150. Resistor Rf 2191 provides feedback between In− 140 and In+ 2130.Switchable resistor Rf 2188 provides feedback between Out+ 520 and Out−2160. Resistor 2189 provides feedback between Out+ 520 and Out− 160.Switchable resistor Rf 2186 provides feedback between Out+ 524 and Out−2160. Resistor 2187 provides feedback between Out+ 524 and Out− 160.

FIG. 22 is an exemplary buffer circuit that could be used for Buffer2104. Buffer 2200 is powered by Power Supply 2290, grounds to Ground2292, and includes n-type transistors N1 2210 and N2 2220, along withp-type transistors P1 2212 and P2 2222.

The drain for N1 2210 connects to Power Supply 2290. Power Supply 2290also connects to Resistor 2280, which then connects to the gate of N12210. The gate of N1 2210 is also connected to In+ 2130. In+ 2130 andthe gate of N1 2210 connect to Capacitor 2263, which then connects tothe gate of P1 2212. The gates of N1 2210 and P1 2212 are also connectedby Resistor 2285. The gate of P1 2212 is also connected to Ground 2292.

The source of N1 2210 is connected to Out+ 2132. The source of N1 2210is also connected to Capacitor 2260, which then connects to the sourceof P1 2212. The sources of N1 2210 and P1 2212 are also connected byResistor 2284. The drain of P1 2212 is connected to Ground 2292.

The drain for N2 2220 connects to Power Supply 2290. Power Supply 2290also connects to Resistor 2281, which then connects to the gate of N22220. The gate of N2 2220 is also connected to In− 2140. In− 2140 andthe gate of N2 2220 connect to Capacitor 2262, which then connects tothe gate of P2 2222. The gates of N2 2220 and P2 2222 are also connectedby Resistor 2282. The gate of P2 2222 is also connected to Ground 2292.

The source of N2 2220 is connected to Out− 2142. The source of N2 2220is also connected to Capacitor 2261, which then connects to the sourceof P2 2222. The sources of N2 2220 and P2 2222 are also connected byResistor 2283. The drain of P2 2222 is connected to Ground 2292.

Resistor 2286 connects Ground 2292 to the gate of P1 2212 and to thesides of Capacitor 2263 and Resistor 2285 not connected to In+ 2130.Resistor 2287 connects Ground 2292 to the gate of P2 2222 and to thesides of Capacitor 2262 and Resistor 2282 not connected to In− 2140.

Buffer 2200 is not limited to use in circuits explicitly describedherein. Buffer 2200 can be used in a wide variety of amplifiers havingnested feedback circuits, and is particularly useful with nestedfeedback circuits that require internal and/or external switching ofresistors in order to change the gain of the amplifier.

FIG. 23 shows an exemplary implementation that has been designedexpressly for single ended input, although in some embodiments, it maybe replicated for use with differential input. LNA Core 2310 featuresthree gain stages, several feedback components, and a bridge. As withother implementations, any number of bridges can be implemented.Feedback circuits (incorporating switchable resistors Rf 312, Rf 562, Rf566, Rf 572 and Rf 576) operate as described previously. An exemplarybridge, in this case a single bridge incorporating Tune Block 172,operates as described previously. However, one leg of the bridge isconnected to Ground 2392.

LNA Core 2310 receives single ended input at In+ 2450. Input is receivedinto a single ended common source transconductance element operating asa first gain stage, Gm1 2301. Gm1 2301 also includes a bridge, which isgrounded through Tune Block 172 as shown. In this example, Gm1 2301provides inverted, single ended output.

The single ended output of Gm1 2301 is received into one of the inputsof a second gain stage, a common gate transconductance element Gm2 2302.In some aspects, Gm2 2302 is a cross coupled transconductance element,such as Gm2 1500 or Gm2 1600. In these cases, the cross couplingprovides for the conversion of single ended input (e.g. at In− 512 inFIG. 23) to differential output. In this example, the other input to Gm22302 (i.e. In+ 522) is connected to Ground 2392.

The gain stages of LNA Core 2310 can also be described as a first stagecomprising a voltage to current converter (i.e. Gm1 2301) and a secondstage comprising a current to voltage converter (in this example, thecombination of Gm2 2302 and Gm3 303), in which the current to voltageconverter also performs a single ended to differential conversion. Thiscombination of a voltage to current converter followed by a current tovoltage converter is not limited to the number and/or type of gainstages shown in FIG. 23. Additionally, a variety of tuning optionsdescribed elsewhere herein can be incorporated in any of theseconfigurations to provide for tuned amplification.

Optionally, circuitry that has been developed for differential input canbe modified for single ended input according to various embodiments.

FIG. 24 is an example of a common source transconductance element thatcan be appropriate for use as Gm1 2301. Gm1 2400 is designed for singleended input, although it could be replicated to accommodate differentialinput. Gm1 2400 is powered by Power Supply 2490 and is grounded byGround 2492. ISource 2491 supplies current. Signal input is received atIn+ 2430, and output is via Out+ 2450.

In+ 2430 is connected to Capacitor 2460, which is then connected to thegate of n-type transistor N1 2410. The gate of N1 2410 is connected tothe drain of N1 2410 via Resistor 2480. The drain of N1 2410 is alsoconnected to ISource 2491, which is connected to Power Supply 2490. Thedrain of N1 2410 is also connected to Out+ 2450. The drain of N1 2410 isalso connected to Resistor 2481, which then connects to the gate ofn-type transistor N2 2420. The source of N1 2410 connects to the drainof N2 2420. The gate of N2 2420 is connected to the source of N2 2420via Capacitor 2461. The source of N2 2420 is grounded to Ground 2492.

Bridge 2470 connects the source of N1 2410 and drain of N2 2420 tocapacitor Capacitor 2462. Capacitor 2462 then connects to Tune Block172. Tune Block 172 then connects to Ground 2493. Ground 2493 can be thesame ground as Ground 2492, but in some embodiments it may beadvantageous to make Ground 2493 the same ground as that grounded to byan antenna (not shown) used to receive signals. As described elsewhere,Tune Block 172 can have an impedance if tuned amplification is desired.For broadband amplification, Tune Block 172 can be a short circuit toGround 2493. In this implementation, N1 2410 substantially providesamplification while N2 2420 substantially provides ground rejection.

In some aspects, N2 2420 can be replaced by a resistor. This replacementwould obviously include the removal of the connection between the gateof N2 2420 and the junction between Capacitor 2461 and Resistor 22481.

FIG. 25 is another example of a common source transconductance elementthat is appropriate for a single ended input into a first stage such asGm1 2301. Gm1 2500 is designed for single ended input, although it couldbe replicated to accommodate differential input. Gm1 2500 shares severalcomponents with Gm1 2400, which are replicated in FIG. 25. However, Gm12500 differs in several aspects.

Gm1 2500 incorporates a third, p-type transistor, P1 2512. The source ofP1 2512 connects to Power Supply 2491. The source of P1 2512 alsoconnects to Capacitor 2564, which then connects to Bridge 2470 betweenCapacitor 2462 and Tune Block 172. Resistor 2480, Out+ 2450, Resistor2481 and the drain of N1 2410 do not connect to ISource 2491 as they doin Gm1 2400. Instead, the drain of N1 2410 is connected to the drain ofP1 2512. These drains are connected to Out+ 2450. These drains are alsoconnected to Resistor 2481, which then connects to the gate of N2 2420and to Capacitor 2461. The drains of N1 2410 and P1 2512 also connect toResistor 2480, which then connects to the gate of P1 2512 and the gateof N1 2410. This implementation features a combination of n-type andp-type amplification.

FIG. 26 shows a schematic diagram of several embodiments. Whereas otherfigures showed differential versions of separate gain stages, biascircuits, transconductance elements, feedback circuits and the like onseparate figures, FIG. 26 incorporates several of these features intoone schematic. This example is not meant to be limiting. Rather, it isjust an alternate way to show how different components can interact. Forsimplicity, FIG. 26 is drawn as a “half circuit” that can function as abroadband current to voltage converter with a single ended input.However, the circuit in FIG. 26 is drawn in a way to suggest replication(e.g. mirroring of the circuit) to create a circuit for differentialinput, and several optional modifications directed toward thisreplication are included in the description of FIG. 26. FIG. 26 alsoshows one combination of n-type and p-type transistors, NLoad and PLoad,and bias circuitry that can create a linear transconductance element(when mirrored to make a differential circuit).

FIG. 26 is a schematic of an inverting, broadband current to voltageconverter incorporating first and second gain stages, bias circuits,feedback circuits, transistor loading circuits and optional crosscoupling circuits. BBI2V 2600 is powered by Power Supply 2690 andgrounds to Ground 2692. BBI2V 2600 features n-type transistors N1 2610,N2 2620, N3 2630, N4 2640 and N5 2650, along with p-type transistors P12612, P2 2622, P3 2632 and P4 2642.

The source of P2 2622 connects to Power Supply 2690. The gate of P2 2622connects to Resistor 2680, which then connects to the drain of P2 2622.The gate of P2 2622 also connects to optional Capacitor 2668, which thenconnects to Power Supply 2690 and the source of P2 2622. The drain of P22622 is also connected to the drain of N4 2640, and both of these drainsare connected to the gate of P4 2642.

The source of N4 2640 connects to the source of P3 2632. These sourcesare connected to In 2412, and also connect to Resistor 2685, which thenconnects to Out 2550. The drain of P3 2632 connects to the drain of N32630. The drains of P3 2632 and N3 2630 connect to the gate of N5 2650.These drains also connect to Resistor 2681, which then connects to thegate of N3 2630. The source of N3 2630 connects to Ground 2692. The gateof N3 2630 also connects to optional Capacitor 2666, which then connectsto Ground 2692 and the source of N3 2630.

Gate bias for N4 2640 is via N1 2610, and gate bias for P3 2632 is viaP1 2612. The drain of N1 2610 is connected to current source ISource2691, which is connected to Power Supply 2690. The drain of N1 2610 isalso connected to the gate of N1 2610. The gate and drain of N1 2610 areconnected to the gate of N4 2640 via optional Resistor 1483 (optionsdiscussed below).

The source of N1 2610 is connected to the source of P1 2612. Thesesources are also connected to Resistor 2682, which connects to the gateof N2 2620. This junction between Resistor 2682 and the gate of N2 2620is also connected to Capacitor 2664, which then connects to Ground 2692.The gate of P1 2612 is connected to the drain of P1 2612. The gate anddrain of P1 2612 are connected to the gate of P3 2632 through optionalResistor 1482. The drain of P1 2612 is connected to the drain of N22620. The source of N2 2620 is connected to Ground 2692.

The source of P4 2642 is connected to Power Supply 2690. The drain of P42642 connects to the drain of N5 2650. These drains are connected toboth Out 2550 and to Resistor 2685 on the side of Resistor 2685 oppositethe connection to In 2412. The source of N5 2650 connects to Ground2692.

The gate of P4 2642 is connected to the gate of N5 2650 via a serialconnection of pairs of a resistor and capacitor connected to each otherin parallel (as shown in FIG. 26). The gate of P4 2642 is connected toboth Resistor 2683 and Capacitor 2660. The opposite sides of bothResistor 2683 and Capacitor 2660 are connected to Junction 2699. Thegate of N5 2650 is connected to both Resistor 2684 and Capacitor 2662.The opposite sides of both Resistor 2684 and Capacitor 2662 areconnected to Junction 2699. Junction 2699 also connects to Resistor2686, which then connects to the drains of both N5 2650 and P4 2642.

FIG. 26 shows examples of two separate gain stages. Although theembodiments shown in FIG. 26 can be used as is, it may be instructive todescribe several of the features of BBI2V 2600 in the context of otherparts of this description. Thus, the first gain stage of BBI2V 2600 (acommon gate linear transconductance element) can be described as asecond gain stage Gm2 for illustrative purposes. Similarly, the secondgain stage of BBI2V 2600 (a common source transconductance element) canbe described as a third gain stage Gm3 for illustrative purposes.Following this illustrative nomenclature, BBI2V 2600 includes a secondgain stage Gm2 (including N4 2640 and P3 2632), bias circuit (includingN1 2610, N2 2620 and P1 2612), third gain stage Gm3 (including P4 2642and N5 2650), NLoad circuit (including N3 2630 and Resistor 2681), PLoadcircuit (including P2622 and Resistor 2680), cross coupling circuit(including Capacitors 1560 and 1568 and Resistors 1483 and 1482) andfeedback components (including Resistors 2683, 2684, 2685, 2686 andCapacitors 2660 and 2662, along with optional Capacitors 2666 and 2668).FIG. 26 shows slightly different embodiments of the common gate andcommon source transconductance elements comprising the gain stages.These embodiments of transconductance elements are not restricted to usein the context of BBI2V 2600.

For some differential input applications, Capacitors 2666 and 2668 maynot be required. However for single ended applications, theincorporation Capacitors 2666 and 2668 may be advantageous. If a“single” version of BBI2V 2600 is to be used “as is” for a single endedinput, or if the replicated or doubled version of BBI2V 2600 is to beused for single ended input (e.g. converting single ended input into adifferential output), including Capacitors 2666 and 2668 can beadvantageous.

For simplification of this alternate view of several embodiments, BBI2V2600 is shown as a “half circuit” as previously described. However,replication of this BBI2V 2600 foreseen, and the replicated versioncould incorporate a cross coupling circuit if either noise cancellationor single ended to differential conversion is desired of the replicatedcircuit (e.g. dual version of BBI2V 2600). Thus, several optionalfeatures are shown on FIG. 26 that can be used to create cross couplingcircuits if so desired. Optional Resistors 1482 and 1483, along withoptional Capacitors 1560 and 1568 would be incorporated as shown tocreate across coupled circuit (comprising two mirrored copies of BBI2V2600). The sides of Capacitors 1560 and 1568 not shown would then beconnected to the sources of the mirrored circuit. Similarly, themirrored version (having the same replicated versions of Resistors 1482and 1483, along with Capacitors 1560 and 1568) would connect to In 2412on FIG. 26.

FIG. 26 provides additional information directed toward severalembodiments. The circuitry including N1 2610, N2 2620 and P1 2612 is abias circuit, and this bias circuit provides gate bias to N4 2620 and P32632. The first gain stage in BBI2V 2600 (which would correspond to asecond gain stage or Gm2 stage in other LNA embodiments) includescircuitry including N4 2620 and P3 2632. One embodiment of NLoad 630 isshown in the circuitry which loads N4 2640. This loading circuitryincludes P2 2622, Resistor 2680 and optional Capacitor 2668. In someapplications, Capacitor 2668 can help ensure that the resistancepresented by the loading circuit is sufficiently high. One embodiment ofPLoad 632 is shown in the circuitry which loads P3 2632. This loadingcircuitry includes N3 2630, Resistor 2681 and Capacitor 2666.

For a replicated (i.e. mirrored) version of BBI2V 2600, the combinationof loading circuits, bias circuits and gain circuits forms an embodimentof a broadband current to voltage converter capable of receiving (e.g.)a differential input.

A variety of resistive circuits and/or resistors could be used for NLoadand PLoad circuitry, as long as they are sufficiently resistive, supplycurrent, and are not current limiting. However the circuitry shown inFIG. 26 may provide for relatively increased headroom as compared toother loads (e.g. resistors).

In some cases, it may be advantageous or efficient to combine thefunctionality of several embodiments onto one circuit or set ofcircuits. In addition to functioning as loading circuits, the circuitsassociated with P2 2622 and N3 2630 also act as bias circuits for thefinal gain stage. Thus, bias for P4 2642 is set by circuitry includingP2 2622 (via the drain of P2 2622), and the bias for N5 2650 is set bycircuitry including N3 2630 (via the drain of N3 2630).

FIG. 27 is a schematic of a common source transconductance elementaccording to one embodiment of the invention. For clarity, the sourcesof DC gate bias are not shown. Various components of CSTE 2700 have beendescribed previously. Certain embodiments of circuits such as the oneshown in FIG. 27 may not require a current source.

FIG. 28 is a schematic of a common gate transconductance elementaccording to one embodiment of the invention. For clarity, the sourcesof DC gate bias are not shown. Various components of CSTE 2800 have beendescribed previously. Certain embodiments of circuits such as the oneshown in FIG. 27 may not require a current source.

FIG. 29A is a block diagram of a common source transconductance elementincorporating a bridge and feedback circuits. CSTE 2901 shows severaloptional locations for the incorporation of tune blocks and capacitorsfor providing tuning if desired. The exemplary transconductance elementGm1 301 is configured to receive a differential input in this example.The connections between Bridge 170 and Gm1 301 are shown in a differentpart of Gm1 301 than other diagrams. This difference is for illustrativeclarity only.

FIG. 29B is a block diagram of a common source transconductance elementincorporating a bridge and feedback circuit. CSTE 2902 shows severaloptional locations for the incorporation of tune blocks and capacitorsfor providing tuning if desired. The exemplary transconductance elementGm1 2301 is configured to receive a single ended input and providedifferential output in this example. The connection between Bridge 170and Gm1 2301 is shown in a different part of Gm1 2301 than otherdiagrams. This difference is only for illustrative clarity.

FIG. 30 is a block diagram of a broadband voltage to voltage converteraccording to an embodiment. BBV2V 3000 includes Gm1 301 and broadbandvoltage to voltage converter BBI2V 3010. BBV2V 3000 also shows severalfeedback circuits and a bridge. This block diagram illustrates severaloptions for the incorporation of tuning circuits if so desired—intoinput circuits, into the bridge, and into feedback circuits.

FIG. 31A is a block diagram showing a combination of an exemplary commongain transconductance element with a feedback circuit. Switchablefeedback resistors Rf 3162 and Rf 3164 provide feedback between eachinput of Gm2 302 and the output having opposite polarity.

FIG. 31B is a block diagram showing an exemplary broadband voltage tovoltage converter (e.g. for use in BBI2V 3010) incorporating feedbackcircuits. BBI2V 3100 includes a common gain transconductance element Gm2302 and a common source transconductance element Gm1 301. Input isreceived by Gm2 302, which then sends signal to Gm1 301, which thencreates output. Switchable feedback resistors Rf 3160, 3162, 3163 and3164 are incorporated into feedback circuits connecting the each inputof each transconductance element to the output having opposite polarity.

In some embodiments, circuitry such as that shown in FIGS. 31A and 31Bmay offer noise reduction, reduced input resistance, and the conversionof single ended input to a differential output. Cross coupling may alsobe incorporated into such circuits.

The above description is illustrative and not restrictive. Manyvariations of the invention will become apparent to those of skill inthe art upon review of this disclosure. The scope of the inventionshould, therefore, be determined not with reference to the abovedescription, but instead should be determined with reference to theappended claims along with their full scope of equivalents.

1. A cross coupled transconductance element having an input and anoutput, the transconductance element comprising: first and secondtransconductance circuits, each transconductance circuit comprising: ann-type transistor having a shared connection, a load-facing connectionand a third connection; a p-type transistor having a shared connection,a load-facing connection and a third connection, the shared connectionof the n-type transistor connected to the shared connection of thep-type transistor; one or more loads, each load connected to theload-facing connection of either the n-type transistor or the p-typetransistor, each load allowing passage of a current; and a capacitiveelement having a first connection and a second connection; the firstconnection of the capacitor connected to the load-facing connection ofthe n-type transistor and the second connection of the capacitorconnected to the load-facing connection of the p-type transistor; afirst bridge connecting a third connection in the first transconductancecircuit to a shared connection in the second transconductance circuit;and a second bridge connecting a third connection in the secondtransconductance circuit to a shared connection in the firsttransconductance circuit, wherein the input is connected to a sharedconnection and the output is connected to the load-facing connection ofat least one transistor that is connected to a load.
 2. Thetransconductance element of claim 1, further comprising a tune blockhaving an impedance, the tune block connected to a bridge, input oroutput.
 3. The transconductance element of claim 2, further comprising asubstrate upon which the transistors are fabricated, and wherein thetune block is external to the substrate.
 4. The cross coupledtransconductance element of claim 1, wherein the shared connection is asource, the load-facing connection is a drain, and the third connectionis a gate.
 5. The cross coupled transconductance element of claim 1,wherein the one or more loads include(s) an active load.
 6. The crosscoupled transconductance element of claim 1, wherein the one or moreloads includes a transistor.
 7. The cross coupled transconductanceelement of claim 1, wherein the one or more loads includes a capacitor.8. The cross coupled transconductance element of claim 1, wherein theone or more loads includes a resistor.
 9. The cross coupledtransconductance element of claim 1, wherein the capacitive elementincludes a capacitor having a first connection and a second connection,the first connection of the capacitor is connected to the firstconnection of the capacitive element, and the second connection of thecapacitor is connected to the second connection of the capacitiveelement.
 10. The cross coupled transconductance element of claim 1,wherein the first and the second transconductance circuit each furthercomprise an input capacitive element having a first connection and asecond connection, wherein the first connection of the input capacitiveelement is connected to the input and the second connection of the inputcapacitive element is connected to the shared connection of the n-typetransistor and to the shared connection of the p-type transistor. 11.The cross coupled transconductance element of claim 10, wherein theinput capacitive element includes a capacitor having a first connectionand a second connection, the first connection of the capacitor isconnected to the first connection of the input capacitive element, andthe second connection of the capacitor is connected to the secondconnection of the input capacitive element.